Phthalocyanines have much promise as photosensitizers for photodynamic therapy, a therapy applicable to cancer treatment. It is now apparent that several promising new types of phthalocyanine or phthalocyanine-like photosensitizers can be made. This has led to the present proposal. The goal of the first part of this proposal is to design, synthesize and characterize new photosensitizers for PDT that are particularly efficient or that can be easily bioeliminated. All the photosensitizers are or contain phthalocyanine or phthalocyanine-like macrocycles. The goal of the second part of the research is to obtain basic information as to the efficiency with which the new compounds transduce photoenergy into chemically reactive species that will initiate photodynamic damage. To achieve this objective a series of photophysical and photochemical studies will be done on the new compounds. These studies will be focused mainly on compounds which have modified phthalocyanine rings, since it is anticipated that the intrinsic photosensitizing capability of the phthalocyanine chromophore in them will vary in important ways from compound to compound.